The present invention is directed to a crop width measuring assembly for measuring the width of crop received by a harvesting assembly of an agricultural machine.
Crop management decisions are increasingly based on the information presented in yield maps. Thus, it is important that they are accurate and contain as few errors as possible. However, two systematic errors occur in existing methods of producing yield maps caused by difficulties in defining the start and end of cutting and knowing the crop width entering the agricultural machine. In order to produce error-free yield maps it is necessary to have an accurate and reliable method of detecting the start and end of harvesting and the width of newly harvested material entering the agricultural harvester.
One existing method of detecting the start and end of cutting is to monitor whether the harvesting assembly is raised or lowered (U.S. Pat. No. 5,524,424 A, EP 0 960 558 A). However, its accuracy depends on the operator""s ability to lower and raise the table at a constant distance from the edge of the standing crop. Other methods have been used for measuring crop flow, but as currently conceived they are unreliable.
Some harvesters have a set of buttons that allow the operator to record the proportional width of the harvesting assembly being full of crop. If the operator does not use these buttons consistently and accurately, then it will cause further errors (S. Blackmore and M. Moore, Remedial Correction of Yield Map Data, Precision Agriculture, 1999, Kluwer, Vol. 1, pages 53-66).
An automatic measurement of the swath width by means of ultrasonic sensors and a determination of the effective harvest area from combine position data generated using GPS is discussed by K. Sudduth et al, Ultrasonic and GPS Measurement of Combine Swath Width, ASAE Annual International Meeting, Orlando, Fla., USA, 12-16 Jul. 1998, ASAE Paper No 983096.
In EP 0 960 558 A, a method for generating yield maps is proposed, in which the presence of crop to be harvested in front of a harvesting assembly is indicated by a sensor monitoring the position of the reel on the combine""s harvesting platform. Additionally, ultrasonic distance sensors measure the width of the harvested crop swath. Thus, on both side ends of the harvesting assembly, ultrasonic distance sensors submit ultrasonic waves to the swath, and the swath width is determined based on the run time of the ultrasonic waves. This method does not work reliably when two swaths with a space between them are taken up. In addition, the ultrasonic sensors do not work when the crop is lodged.
DE 195 43 343 A discloses a baler in which the volume of received crop is measured by a capacitive sensor. DE 40 41 995 A proposes a forage harvester in which presence of crop throughput is detected by means of a capacitive sensor. According to the signal of the sensor, the rotational speed of the chopping drum of the forage harvester is controlled, or conservation chemicals are added to the harvested crop.
It is an object of the present invention to provide an apparatus for establishing a yield map having improved precision and reliability.
To accomplish this objective, a number of crop presence sensors are distributed over the width of a harvesting assembly of the agricultural machine. Preferably, the crop presence sensors are evenly distributed along the width of the harvesting assembly. It would also possible to have an uneven distribution. Each one of the crop presence sensors is capable of detecting whether crop is present in its detection range. The size of the detection range depends on the type of the crop presence sensor. It is possible to use crop presence sensors having a relatively large detection range, such as ultrasonic sensors covering a part of the width of the harvesting assembly, or to use crop presence sensors with a relatively small detection range. The latter only detect crop passing in their vicinity. According to the signals of the crop presence sensors, the crop width measuring assembly is operable to establish information regarding the width of the crop actually being received by the harvesting assembly. The actual swath width can be calculated by adding the width of the detection ranges of the crop presence sensors detecting crop (when the detection range is relatively large), or by multiplying the distance between adjacent sensors with the number of sensors detecting crop.
An advantage of the present invention is that cheaper and more reliable sensors can be used, since the distance between a sensor and the edge of the crop swath is not measuredxe2x80x94like in the prior art, EP 0 960 558 Axe2x80x94but rather only the presence or absence of crop is detected. When the number of crop presence sensors is sufficiently high, the accuracy of the crop width measuring assembly is comparable with, or even higher than, the accuracy of known ultrasonic sensors for measuring swath width. Furthermore, the crop width measuring assembly according to the present invention is capable of detecting actual swath width when two swaths having a gap are received by the harvesting assembly.
Possible errors in the established swath width could be due to crop remaining in the detection range of the crop presence sensors. Such crop should not influence the information provided by the crop presence sensors. In order to resolve this problem, it is proposed to arrange the crop presence sensor such that moving crop removes (wipes) any stationary crop away from the crop presence sensors. This can be achieved when the outer surface of the crop presence sensor is located in the plane of the surface of the table of the harvesting assembly.
Alternatively or additionally, the signals from the crop presence sensors can be electronically processed by means of a signal processor to remove the effect of any stationary crop actuating the crop presence sensor. Thus, the output signal of the crop presence sensor can be time differentiated and afterwards submitted to a comparator or Schmidt-Trigger.
Capacitive sensors are preferably used as relatively cheap and compact crop presence sensors having a small detection range. They also work in conditions when crop is lodged.
The crop width measuring assembly of the present invention can be used in conjunction with a processor for collecting data concerning additional crop parameters. The processor is provided with a geographic position sensor, such as a GPS sensor and/or a speed sensor. In order to establish accurately the crop parameters with the geographic location, information regarding the crop swath width is necessary. The swath width sensor of the present invention establishes this information. Thus, the disadvantages of conventional hectare countersxe2x80x94dependence on position of the header and unknown swath width, see U.S. Pat. No. 5,524,424 Axe2x80x94are avoided.
Preferably, the apparatus for collecting data is operable to establish a yield map. Thus, an additional crop parameter sensor measuring a parameter of the crop received (such as weight per time or moisture content) is delivered to the processor. From this data, the processor establishes a map representative of the parameter at several locations of the field. This parameter can be the weight of the received crop per area, which is calculated according to the measured received weight per time, the swath width and the speed or position of the agricultural machine. The area is calculated using the signals from the crop width measuring assembly. Hence, errors in the yield map due to unknown swath widthxe2x80x94as described abovexe2x80x94are avoided.
The signals from the crop presence sensors can also be used to determine whether crop is received at all, and thus yields information defining the start and end of the harvesting cycle. An accurate definition of when harvesting starts and stops is as important as measuring crop width in producing an accurate yield map. Unless at least one crop presence sensor indicates the presence of crop, the yield established by the processor is considered as zero.
The present invention can be used in any type of harvesting assembly used on any type of agricultural machine. Preferably, it is used on a combine, wherein the crop presence sensors are distributed over the active width of a cutter bar of the harvesting assembly for a combine. It could also be used in a forage harvester, the sensors distributed over the width of the forage harvester harvesting assembly. Use of the invention on other harvesting assemblies such as mowers and any other agricultural machine processing, receiving, taking up or harvesting crop is also possible.